Two analysts value the same manufacturer, agree on every cash flow, and disagree on price by 30%. The gap is entirely in the discount rate, and almost all of it comes from four judgment calls about the equity risk premium.
A company's weighted average cost of capital (WACC) blends the after-tax cost of each financing source at its target weight.
Three inputs carry all the estimation risk: which method computes each cost, what the target capital structure is, and what marginal tax rate applies. The marginal rate, not the average or effective rate, is the right one, because it prices the tax shield on the next dollar of interest.
Top-down drivers are systematic and reach the company through the risk-free rate, aggregate credit spreads, and the equity risk premium.
- Capital availability: deep, liquid markets with stable currencies and strong property rights lower perceived risk, narrowing spreads.
- Market conditions: credit spreads and the equity risk premium widen in recessions and tighten in expansions. Higher inflation lifts the risk-free rate; higher exchange rate volatility lifts required returns.
Common mistakes
- Using the coupon rate as the cost of debt. Kestrel's cost of debt is the 6.10% synthetic-rating yield, not whatever rate its existing loans carry. Cost of capital is always marginal.
- Tax-adjusting the wrong components. Only interest is deductible. Preferred dividends at 6.50% enter WACC untaxed, and if a company has already hit an interest deduction cap, the debt cost takes no tax haircut either.
- Forgetting to unlever before relevering. Applying the peer's 1.30 equity beta directly to Kestrel imports the peer's 0.50 D/E, overstating cost of equity by roughly 25 bp here and far more when peer leverage diverges.
Bottom line
- WACC formula: weight of debt times after-tax cost of debt, plus weight of preferred times its cost, plus weight of equity times required return on equity, at market-value target weights and the marginal tax rate
- Top-down factors: capital availability, market conditions, legal and regulatory environment plus country risk, tax jurisdiction
- Bottom-up factors: cash flow volatility, asset tangibility and liquidity, financial strength and leverage, security features, ESG risk
- Security features: callability raises cost of debt at issuance; putability and convertibility lower it; cumulative preferred costs less than non-cumulative
Exam shortcut
Read the stem for the word "private." That single word switches you from traded-YTM plus CAPM to synthetic rating plus unlever-relever plus size and specific premia, and it is the most reliable branch signal in this reading. "Recently issued bank loan" means use that loan's rate; "no rating" means build a synthetic one; "lease" means the implicit rate, falling back to the incremental borrowing rate.
The full lesson (about 3,778 words, 25 min read) adds 8 worked examples, all 6 common mistakes, a self-check, free in the app.
Learning objectives
- cost of capital
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